1. Field of the Invention
The present invention relates to technology for correcting a mask pattern, more particularly, to a method for correcting a mask pattern, a system for correcting a mask pattern, program, a method for manufacturing a photomask and a method for manufacturing a semiconductor device.
2. Description of the Related Art
In recent years, technologies for manufacturing semiconductor integrated circuits have made very remarkable progress, and semiconductor integrated circuits with a minimum size of 0.13 μm are mass produced. Feature size of the semiconductor integrated circuits has been decreased by the rapid progress of the technology to form micropatterns including a mask process technology, photolithography technology, and etching technology. In a period when the pattern size was large enough, a planar shape of a device pattern desired to be formed on a wafer was drawn as a design pattern with no modification, and a mask pattern true to the design pattern was formed. The mask pattern was then transferred onto the wafer by a projection optical system to process a substrate. The device pattern can therefore be formed to be substantially identical to the design pattern.
However, the progress in decrease of pattern size has caused a problem that the size of the device pattern is not identical to the size of the design pattern. Accordingly, processing (hereinafter, referred to as “mask data processing”) to correct a mask pattern so that the size of the device pattern is equal to the size of the design pattern has become very important. For performing the mask data processing, an optical proximity correction (OPC) process to correct the optical proximity effect (OPE) is known.
In recent years, along with the reduction in size of the device pattern, a k1 value (k1=W/(NA/λ), where W represents design size, λ represents exposure wavelength, and NA represents numerical aperture of a projection lens) of a lithography process is continuously decreased. Accordingly, the OPE tends to further increase, and load on the OPC process becomes very large. As a method to achieve high accuracy in the OPC processing, a “model-based OPC” is favored, which predicts the OPE using a illumination intensity simulator and corrects a mask pattern.
In the model-based OPC, the mask pattern is corrected such that the size of the device pattern is identical to the size of the design pattern under a particular process condition of a best focus value or the like. When the particular process condition is no longer satisfied during transfer of the mask pattern to form the device pattern, the size of the device pattern sometimes varies, and a desired specification of a device implemented by the device pattern cannot be achieved. To achieve the desired specification, the device pattern must be formed under the particular process condition, and a sufficient process margin cannot be ensured.